Micromirrors may be used in various optical applications instead of, or in addition to, conventional optoelectronic devices. It is desirable to be able to move the micromirrors by rotation and translation with very fine control.
A phase-only piston-style micromirror has been used for phase adaptive optics applications and a rotational micromirror has been used to deflect light. Most of these micromirrors have been controlled to have continuous displacements, which are determined at the equilibrium between electrostatic force and elastic force. The analog control is more complex than the digital or discrete control, and is not compatible with known semiconductor electronics technologies such as MOS, CMOS, etc. In addition, the micromirrors with continuous displacement actuated by electrostatic force undergo the classical snap-down phenomenon when the electric force exceeds the elastic force of mechanical structure. The snap-down phenomenon limits the translational and rotational ranges of a micromirror.
The high driving voltage is another disadvantage in use of the micromirrors with continuous displacement actuated by electrostatic force. To be compatible with IC components, it is desired that micromirrors are operated at low voltage which is compatible with the circuit operation or control voltage.
In a prior art micromirror array, such as, for example, the Digital Micromirror Device in U.S. Pat. Nos. 4,566,939, 5,083,857, and 6,232,936, each micromirror is actuated by digital control of a voltage. It has large rotation, low driving voltage, and is compatible with known semiconductor electronics technologies. However, it has only one degree of freedom, that is, rotation about a single axis, and it only has two level positions. Therefore, the micromirror array is merely an array of optical switches.
Therefore, what is needed is a system and method for very delicate control of the micromirror rotation and translation movement.